function fnInit() {
   oDiv.style.setExpression("left",
      "document.body.clientWidth/2 - oDiv.offsetWidth/2"
   );

   oDiv.style.setExpression("top",
      "document.body.clientHeight/2 - oDiv.offsetHeight/2"
   );
   document.recalc(true);
}

function changeColor(obj,color) {
	obj.style.backgroundColor = color;
}